(1) Field of the Invention
This invention relates to a system and a method for controlling the positioning of bubbles in a liquid medium using acoustic energy waves, and more particularly, to a system and a method for producing solid mass with an arrangement of voids imbedded within the article.
(2) Description of the Prior Art
Conventional systems for controlling the positioning of bubbles or particles in a liquid medium as, for example, those described in U.S. Pat. No. 4,759,775, comprise transducers which convert electric energy into acoustic energy and transmit acoustic energy waves at various frequencies. The interaction of a pair of the transducers or a transducer and a reflector reflecting the acoustic energy waves from the transducer will establish a standing wave field. The bubbles or particles which were scattered in the liquid medium migrate to nodes and antinodes of the standing wave. Generally, the denser bubbles or particles move to nodes where regional pressures are minimal, and the lighter bubbles or particles move to antinodes where regional pressures are maximum. In this fashion, the bubbles or particles with dissimilar densities can be segregated from the liquid medium using a process known as "frequency sweeping".
Because bubbles can collect at both nodes and antinodes, the location where the bubbles collect is identified as a nodal line or standing domain. However, the conventional systems for controlling the positioning of bubbles or particles using the acoustic energy waves do not position the bubbles or particles in the liquid medium in a desired sequence or arrangement, such as a two-dimensional or three-dimensional grid form. The conventional systems also do not uniformly control the sizing and spacing of the bubbles or particles positioned in the standing wave field within the medium.
The conventional systems and methods for moving bubbles are also limited to a liquid medium and are not capable of producing a solid article having voids of a predetermined size and spacing. Other conventional processes used to produce a large number of uniform holes in a solid medium, such as metal matrix production or sterolithography, are relatively expensive and slow.